EgyptSat-1 (also referred to as Misrsat-1) is an international collaborative minisatellite project of NARSS (National Authority for Remote Sensing and Space Science) of Egypt and the Yuzhnoye State Design Office (YSDO), Dnepropetrosvk, Ukraine. In 2001, Yuzhnoye won the contract to design and develop the satellite, providing also technical expertise and on-the-job training to 60 Egyptian engineers and experts as well as technology transfer.

The industrial consortium consisted of Ukrainian companies with Yuzhnoye as as prime contractor responsible for the platform and the launch. SSRE "CONECS" was responsible for the development of the two optical payloads, the onboard payload command and data handling subsystem, as well as for the development of the data processing in the ground segment. Subcontractors to SSRE CONECS were "Arsenal" in Kiev for optics manufacturing, SRDI "Elvit" for the onboard data processing and XenICs nv for the SWIR array manufacturing. 1)

EgyptSat-1 is the first remote sensing satellite of Egypt funded by the government of Egypt. The objective is to fly two instruments: a multispectral imager and an infrared imager. 2)3)4)5)

The spacecraft design features a modular bus (frame-type modules). The spacecraft has a launch mass of 165 kg (minisatellite). The design life is 3 years with a goal of 5 years. The EgyptSat-1 spacecraft was developed by the Yuzhnoye State Design Office and produced by the State Enterprise Production Association Yuzhny Machine-Building Plant.

Unfortunately, a description of the spacecraft and its subsystems (published paper) was not available from NARSS.

Figure 2: General layout of the deployed EgyptSat-1 spacecraft without side panels (image credit: NARSS)

The CubeSats were deployed after the primary spacecraft was deployed into a nearly circular polar orbit. Three P-PODs contained the 6 single CubeSats and 1 triple CubeSat for MAST.

Orbit: Sun-synchronous orbit, altitude = 668 km, inclination = 98.1º, period = 98.1 minutes. The local equator crossing time is at 10:30 hours, the revisiting time is ~ 13 days after 191 orbital periods.

RF communications: The S-band is used for TT&C support. The X-band is used to downlink the payload data (imagery). An on-board memory system stores the payload data when not in contact with a station.

The Egyptian satellite stopped communicating on July 19,2010, three years and 3 months after its launch on April 17th 2007. The failure to communicate is believed to have been due to the failure in the S-band transmitter-receiver (TR) unit which is part of the TTC subsystem. The subsystem has a backup TR unit in addition to the main unit. This failure has occurred at least twice before and contact was restored by the satellite operating team. In the last occurrence, communication was transferred to the redundant backup unit and the system resumed operating. It, therefore, appears logical that the reason for loss of contact was the failure of the backup TR unit of the TTC subsystem.

The lessons learned from that experience for future satellites are threefold:

1) Additional redundant components of different type and make. Provide additional redundancy for any unit that has a history, or a high probability of failure. The additional unit must be of different type, and better yet, from a different manufacturer. This reduces the likelihood of the second redundant unit failing due to the same operational reasons as the first one.

2) Provide Fault Tolerance Design algorithms which allow detection of the fault and switching to the alternative path. In a small satellite were reliability is not at its highest level the way to enhance reliability is to provide fault tolerant design from the beginning and in parallel with the original or main design. Fault tolerant designs are many and they differ in philosophy, complexity and cost. One key feature is that they should be autonomously operated but adaptable from ground.

3) Multiple paths for command and telemetry signals. Provide alternative paths to the TTC signals. In our case of EgyptSat-1 design, this could be done through the store and forward payload transmitter which operates on UHF. The telemetry data alone could be downloaded via the X-band link to the ground receiving station.

Attention to storm protection of the ground structure:
On October 19, 2007 a lightning storm hit the site in which the control station was erected. The site was an empty desert site and the station antenna was the highest standing object. Since we never experienced such an event before, the station was not equipped with sufficient lightning protection. Service was transferred immediately to the Ukrainian backup station until the station was repaired and lightning insulated in a number of days. The lesson is that lightning protection is essential, even if the probability of lightning striking your station in the desert is very small.

Too many extra payloads:
In a first satellite experience, especially one that is combined with technology transfer, not too many payloads should be onboard which are not likely to be used. On EgyptSat-1the project had a communication payload with a store and forward device. What we learned is that it takes so much effort in design, testing, integrating and fault detection that burdens and takes away from the main job of the satellite and its main payload. Having extra payloads should be weighed against the efforts put in integrating, testing and operating them.

Training and technology transfer:
Training and acquisition of know-how of a team of engineers in the areas of design, assembly, software development, integration and testing of satellites. This objective was achieved with a large degree of success. In this objective the following was accomplished; training of 64 engineers and Ph.D. holders in all aspects of design, manufacturing, testing, and operation of the satellite. Of those 12 were Ph.D. holders who acted as group leaders.

- Number of trainees: Number of engineers enrolled in this program was larger than most other programs. In similar programs in other countries only 12-24 persons were enrolled. The reasons were to compensate for possible departure of some of the trained engineers and to maintain the technical integrity of the team.

- Level of education at entry: It would have been preferable if we had a larger number of more mature engineers at the M.Sc. level.

- Training at various phases of the project: In all aspects direct training was mixed with participation and technology transfer. The training concentrated on the following aspects, (a) Theoretical training; (b) Design of satellite and subsystems; (c) Manufacturing, assembly and integration; (d) Subassembly and assembly testing; (e) Launch, integration with launch vehicle and satellite commissioning; (f) Operations.

In item (b); acquisition of technology and know-how was at its peak, simply because the engineers were prepared by their education to this type of experience. In item (c), the level of acquisition of technology was much less, because of the nature of the manufacturing process. Our team did not include sufficient industrial and technician elements, which were needed for proper and complete transfer of technology.

Testing and design of test equipment:
One of the important lessons learned in space technology is that (testing) is the most important phase in the space manufacturing process. The EgyptSat-1 team excelled in the testing phase because it occurred after sufficient training and familiarity with the satellite and its components. The design and building of test equipment is as important as the design of the satellite itself. This activity should be performed in parallel and simultaneously with the subsystem design.

Utilization of the images of EgyptSat-1:
The effective utilization of images taken by indigenous satellites in developing countries is an important factor for development of space programs in these nations. Recent trends in space faring developing countries show that space programs in these countries cannot be propelled or sustained based on technological aspects alone. The economic benefits of the space technology and applications are as important in ensuring the societal and governmental support for these programs as the national pride and acquisition of technology. The extent of utilization of satellite images in developing countries is not well documented. — In previous work, we established that in order to assess the extent of utilization of space products there is a need for measuring metrics the extent to which satellite images from different sources are being used in real projects and the extent to which indigenous satellite images have replaced the use of international commercial satellite images. Further attempts to assess the status of utilization of satellite imagery in the developed countries are needed.

Education:
Several new programs for Space Sciences and Technology were initiated in Egyptian universities both governmental and private. The leading and oldest Aerospace undergraduate and graduate program is given at the Aerospace Department at Cairo University (Ref. 7).

• In July 2010, NARSS lost communications and control of the EgyptSat-1 spacecraft. All attempts by NARSS and by Yuzhnoye to regain control of the spacecraft failed so far. NARSS reported this event on October 23, 2010. After 3 years of on orbit operations, the mission of EgyptSat-1 can be regarded as ended.

• On April 10, 2008, the Egyptian ground control station for EgyptSat-1 was inaugurated.

Sensor complement: (MBEI, IREI)

Both instruments were designed and developed at SSRE CONECS in Lviv, Ukraine. This included also the PLCDHS (PayLoad Command and Data Handling System) for on-board data handling, data storage, compression and data transfer to the X-band communication system (Ref. 1). 10)

MBEI (MultiBand Earth Imager):

MBEI is a Pan (panchromatic) and MS (Multispectral) pushbroom imager providing co-registered imagery of the target area in Pan and 3 narrow MS bands within the VNIR (Visible Near-Infrared) spectral region. Some the the spectral bands are identical with those of the Vegetation instrument on SPOT missions.

The compact instrument has a mass of only 26 kg. The power dissipation of the sensors and associated driving and buffering electronics is limited to 25 W. The unit is also equipped with an additional heater of 25 W to stabilize the temperature of the instrument.

The overall objective of the MBEI instrument is to observe the irradiance coming from the soil and the vegetation. The first band (B1) is being used to make atmospheric corrections; the panchromatic channel is present to enhance the situational awareness and to ease the interpretation of the acquired data (Ref. 1).

The objective of IREI is to observe the irradiance form the target area in one SWIR (Short Wavelength Infrared) spectral band. The instrument features one optically butted module, consisting of 3 linear arrays with 500 InGaAs pixels each (Ref. 1).

This instrument is aligned with the MBEI instrument and is operated at 4 times the pitch of the VNIR bands. Due to the increased pitch, the optics is twice as small; the power of the IREI instrument is also lower than that of the higher speed MBEI instrument.

Instrument type

Pushbroom imager

Spectral band

1.55 - 1.7 µm

Spatial resolution at nadir

39 m (cross-track) x 46 m (along-track)

Swath width at nadir

55 km

Spacecraft body pointing capability

±35º (repointing is provided by spacecraft rotation)

FOR (Field of Regard)

980 km

Optics:
Focal length
Diameter of entrance pupil
Lens aperture

430 mm
97 mm
f/4.4

SNR

> 100 (at max. illuminance)

MTF

35%

Detector line array

3 linear arrays with 500 InGaAs pixels each. The detector has a spectral range of 1.1-1.7 µm but IREI has spectral band 1.55 - 1.7 µm due to the optical filter

FPA (Focal Plane Assembly): The FPA of the IREI features a fourfold lower spatial resolution than the imagery of the MBEI instrument. Three linear line InGaAs arrays, consisting of a central PDA (PhotoDiode Array) with 500 pixels, and 2 ROIC (Readout Integrated Circuit) modules are optically butted around a central beam splitter. In this way the needed space is created to accommodate the packaged sensor arrays. To allow the reordering of the pixels in ground processing, there is an overlap of 25 pixels in the butting edge.

The detector arrays are mounted in a modified metal can package. As the instrument ambient is kept constant between 15-25ºC, it is not necessary to introduce a thermoelectric or a Peltier cooler in the package. This measure allowed to reduce the wall height of the package and also the size of the fixation flanges.

The PDA of 500 effective pixels on a pitch of 25 µm is mounted in a metal can which is wire-bonded to 2 CMOS ROICs (with 256 inputs each on a pitch of 50 µm). For the interconnection of the PDA to the ROIC's a double wire bonding layer on a pitch of 100 µm is used. The PDA and the 2 ROICs are placed on a alumina substrate together with 4 resistors, 4 capacitors and 5 kΩ @ 25ºC NTC.

The MBEI and IREI source data, preconditioned by the proximity electronics, are further treated and stored by the PLCDHS. This system is capable of treating a data stream of 48 Mbit/s; it has a storage capacity of 2 GByte. Prior to transmission to the ground station, the data are compressed, combined with telemetry data and formatted. Then the data are sent to the X-band communication unit of the platform.

MBEI source data rate (four bands)
IREI source data rate

~184 Mbit/s
1.92 Mbit/s

Mass memory capacity

2 GByte

Data compression rate range

1.5 - 4

Data output rate to X-band transmitter

30.72 Mbit/s (after application of compression algorithm)

Peak power consumption

< 35 W

Instrument mass, volume

< 7 kg, < 6800 cm3

Table 3: Summary of the PLCDHS instrument parameters

1) Oleg Lapshinov, Viktor Tkachenko, Leonid Varichenko, Jan Vermeiren, "Design, Development and First Assessment of the SWIR Instrument for Remote Sensing on Board of EgyptSat-1," Proceedings of the IAA Symposium on Small Satellite Systems and Services (4S), Rhodes, Greece, May 26-30, 2008, ESA SP-660, August 2008

The information compiled and edited in this article was provided by Herbert J. Kramer from his documentation of: "Observation of the Earth and Its Environment: Survey of Missions and Sensors" (Springer Verlag) as well as many other sources after the publication of the 4th edition in 2002. - Comments and corrections to this article are always welcome for further updates (herb.kramer@gmx.net).